Re: [dpdk-dev] [EXTERNAL] Re: [PATCH v2 1/4] eal: disable function versioning on Windows

[Neil Horman <nhorman@tuxdriver.com>]

On Mon, Jun 01, 2020 at 09:46:18PM +0000, Omar Cardona wrote:
> >> Do we know if we have future plans of supporting dlls on windows in the future?
> 	- Hi Neil, yes this is of interest to us (Windows).  
> 	- Specifically to aid in non-disruptive granular servicing/updating.
> 	- Our primary scenario Userspace VMSwitch is biased towards shared libraries for production servicing
> 
Ok, do you have recommendations on how to provide backwards compatibility
between dpdk versions?  From what I read the most direct solution would be
per-application dll bundling (which seems to me to defeat the purpose of
creating a dll, but if its the only solution, perhaps thats all we have to work
with).  Is there a better solution?

If not, then I would suggest that, instead of disabling shared libraries on
Windows, as we do below, we allow it, and redefine VERSION_SYMBOL[_EXPERIMENTAL]
to do nothing, and implement BIND_DEFAULT_SYMBOL to act like MAP_STATIC_SYMBOL
by aliasing the supplied symbol name to the provided export name.  I think msvc
supports aliasing, correct?
Neil

> 
> -----Original Message-----
> From: Neil Horman <nhorman@tuxdriver.com> 
> Sent: Monday, June 1, 2020 12:56 PM
> To: Fady Bader <fady@mellanox.com>
> Cc: dev@dpdk.org; thomas@monjalon.net; tbashar@mellanox.com; talshn@mellanox.com; yohadt@mellanox.com; dmitry.kozliuk@gmail.com; Harini Ramakrishnan <Harini.Ramakrishnan@microsoft.com>; Omar Cardona <ocardona@microsoft.com>; pallavi.kadam@intel.com; ranjit.menon@intel.com; olivier.matz@6wind.com; arybchenko@solarflare.com; mdr@ashroe.eu
> Subject: [EXTERNAL] Re: [PATCH v2 1/4] eal: disable function versioning on Windows
> 
> On Mon, Jun 01, 2020 at 01:31:36PM +0300, Fady Bader wrote:
> > Function versioning is not needed on Windows, also the function 
> > versioning implementation is not supported by Windows.
> > Function versioning was disabled on Windows.
> > 
> I get that windows doesn't seem to support symbol level versioning, but I'm not sure its reasonable to say that its not needed, unless we never have any intention of building dpdk on windows using a DSO model.  The below definately solves the immediate problem, but if we plan to support windows with dynamic library builds, this just kicks the can down the road.
> 
> Do we know if we have future plans of supporting dlls on windows in the future?
> 
> Neil
> 
> > Signed-off-by: Fady Bader <fady@mellanox.com>
> > ---
> >  lib/librte_eal/include/rte_function_versioning.h | 4 ++++
> >  1 file changed, 4 insertions(+)
> > 
> > diff --git a/lib/librte_eal/include/rte_function_versioning.h 
> > b/lib/librte_eal/include/rte_function_versioning.h
> > index f588f2643..cee06602e 100644
> > --- a/lib/librte_eal/include/rte_function_versioning.h
> > +++ b/lib/librte_eal/include/rte_function_versioning.h
> > @@ -11,6 +11,10 @@
> >  #error Use of function versioning disabled, is "use_function_versioning=true" in meson.build?
> >  #endif
> >  
> > +#ifdef RTE_EXEC_ENV_WINDOWS
> > +#undef RTE_BUILD_SHARED_LIB
> > +#endif
> > +
> >  #ifdef RTE_BUILD_SHARED_LIB
> >  
> >  /*
> > --
> > 2.16.1.windows.4
> > 
> > 
>